Generally, image forming apparatuses such as copiers and printers include an image bearer, such as a drum-shaped or belt-shaped photoreceptor and a drum-shaped or belt-shaped intermediate transfer member, and a cleaning unit to remove any toner remaining on the image bearer after image transfer. The toner removed from the image bearer (i.e., waste toner) is collected in a waste toner container.
Being filled to capacity (or close to the capacity) with the waste toner, the waste toner container is removed from the apparatus body of the image forming apparatus, and then an empty waste toner container is set in the apparatus instead.
For example, US-2007110458-A1, US-2004258441-A1, and JP-2009-63772-A propose waste toner containers shaped like substantially rectangular parallelepipeds and containing a waste toner conveyance member, such as a paddle. The waste toner conveyance member distributes waste toner uniformly and entirely in the waste toner container.
JP-2009-63772-A further proposes a waste toner detector to detect whether the waste toner container is filled to capacity with waste toner. Specifically, an opening formed on the side of the waste toner container is covered with a rubber seal, and a filler is provided outside the waste toner container to contact the rubber seal externally. When the amount of the waste toner collected in the waste toner container reaches a predetermined amount, the rubber sealed is pushed by the waste toner and pushes the filler. The movement of the filler is optically detected by a sensor.
However, if the waste toner container is a substantially rectangular parallelepiped, it is difficult to make full use of the space inside the image forming apparatus and to secure a sufficient capacity of the waste toner container. Accordingly, replacement cycle of the waste toner container is relatively short.
In view of the foregoing, a part of the waste toner container, which typically extends in a depth direction of the apparatus, may be projected upward to effectively use the space inside the apparatus except functional areas, thereby increasing the capacity of the waste toner container. In such a configuration, it is necessary to detect whether the waste toner container including the projecting portion is filled to capacity with toner entirely and detect timely and reliably it when the waste toner container is full.